Horizontal rotating retorts are in common use for pyrolyzing and otherwise processing carbonaceous and noncarbonaceous materials. In general, rotating retorts include a rotating vessel portion which is supported between two stationary retort portions. In the case of carbonaceous material such as oil shale, coal, peat or the like, the material is generally introduced through one stationary retort portion and into the rotating vessel portion. As carbonaceous material is rotated within the rotating vessel portion, heat is applied to the material in the absence of oxygen to pyrolyze the material and recover valuable hydrocarbon products. Due to the production of large volumes of hydrocarbon product gases, the majority of rotating retorts processing carbonaceous material are operated at pressures above atmospheric. The product vapors produced during pyrolysis are removed from the rotating vessel portion out through the other stationary retort portion and transferred to further product processing.
In operation, it is essential that suitable seals be provided between the rotating vessel portion and the stationary retort portions to prevent the escape of valuable product vapors into the atmosphere. Providing adequate seals is particularly difficult due to the large surfaces which must be sealed and high pressures which can be developed during normal retort operation. Since retorts are designed to handle large amounts of material in order to produce commercially acceptable amounts of product vapors, the retorts must necessarily be quite large. Typically, a large annular disc is attached to each end of the rotating vessel portion of the retort. These discs may be formed integrally with the rotating vessel portion or otherwise sealably attached. A suitable seal is then provided between the annular discs and each stationary retort portion. Because of their extremely large size, and due to variations and limitations in processing methods and manufacturing, the annular sealing discs which are generally available do not have perfectly uniform width or annular shape. As a result, during rotation of the rotating vessel, the seal discs tend to nutate and wobble to varying degrees. The disc nutations are generally limited within certain relatively close tolerances; however, it would be very difficult if not impossible to prevent any nutations from occurring.
Common sealing elements which have been utilized for retort seals include rubber, teflon and some more exotic materials. These type of seals are subject to wear and must be replaced continually. The replacement of these large retort seals is costly and time consuming. Further, certain areas along the seals become worn more than others due to nutations of the sealing disc. These excessively worn seal areas provide a weak point in the seal where pressurized product gases may escape from the rotating retort.
It is therefore desirable to provide a retort seal which is not dependent upon seal elements such as rubber or teflon which are subject to wear and continual replacement. It is further desirable to provide a retort seal which is self-compensating or self-aligning on the nutating sealing disc to prevent product liquid and vapor leakage during retort operations.